1. Field of the Invention
The present invention relates to a device for fastening flexible printing plates. More specifically, the present invention relates to a device for fastening flexible printing plates by securing ends of a printing plate in a plate cylinder of a rotary printing machine having a channel, and a bore, where the ends are secured in the channel using securing means.
2. Description of the Related Art
German reference DD 261 765 A1 discloses a device for fastening flexible printing plates to a plate cylinder of rotary printing machines. The device has a channel in the plate cylinder, which accommodates the bent ends of the printing plate, a bore in the channel which is axially parallel to the plate cylinder, two segmented shafts arranged pivotally in the bore and leaf springs which are each fastened to the segmented shafts and can be brought into contact with the ends inserted into the channel. The segmented shafts are mounted in the bore in the channel via a hollow shaft which is cut out for the leaf springs. The ends of the printing plates are bent at different acute angles depending on the direction of rotation of the plate cylinder. A leading end is clamped directly by the leaf springs against an oblique channel side wall. A trailing end is clamped between the leaf springs and a clamping bar fastened to the hollow shaft. The device depends upon the direction of rotation and has a relatively wide channel opening on the periphery of the plate cylinder, because of the double mounting of the segment shafts in the bore. The device requires a correspondingly high outlay, and is not suitable for automated printing-plate changing applications.
The object of the present invention is to provide a device for fastening flexible printing plates which secure the ends of the printing plate in the channel, even during high speed of revolution of the plate cylinder, and to ensure a printing plate change which enables the printing plate to be recycled. It is a further object to provide a fastening device of simple construction that is not susceptible to faults and is suitable for automatic printing plate change operations.
To achieve this object, the device includes a printing cylinder having a channel, a channel gap, at least one lateral cut out (or recess) and a bore. The bore is at a radial terminus of the channel. A segmented shaft is pivotally arranged in the bore. Leaf springs are arranged in the channel and attached to the segmented shaft. The leaf springs may be pressed against bend ends of a flexible printing plate so as to secure the bend ends when they are inserted into the channel.
The invention secures bent ends of the printing plate against slipping out of the channel by a positive and frictional connection produced by the interaction of shaped elements, recesses, contact faces and the leaf springs. Performance is assured even at a high circumferential speed of the plate cylinder. The device according to the present invention can be used irrespective of the direction of rotation with respect to the plate cylinder, and in conjunction with the rectangularly bent ends of the printing plate. It is suitable for automatic printing plate changing, since the insertion and withdrawal of both ends always takes place at the same angle, namely at right angles to the plate cylinder, and does not require any change in the direction of rotation of the plate cylinder. In addition, the printing plate is not damaged during the changing operation, ensuring its multiple use.
The interaction during a printing plate change of shaped elements having a relatively low height, together with the recesses and/or contact faces in the channel, makes it possible to have a narrow channel gap on the periphery of the plate cylinder. This benefits the printing process by minimizing channel impacts. Finally, the direct arrangement of the segmented shafts in the bore of the channel ensures a simple construction of the device, and the indirect support of the segmented shafts via supporting elements, in conjunction with the large clearance between the segmented shaft and the bore, ensures low susceptibility to faults with regard to the mobility of the mechanisms as a result of contamination getting into the channel.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.